Centralized traffic controlling system for railroads



April 5, 1938. w. T. POWELL CENTRALIZED TRAFFIC CONTROLLING SYSTEM FORRAILROADS Filed April 15; 1935 7 Sheets-Sheet 1 mvsmo Z0. .7

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April 5, 193-8. w. T. POWELL I CENTRALIZED TRAFFIC CONTROLLING SYSTEMFOR RAILROADS Filed April 15, 1933 INVENTOR BY a ATTORNEY 7 Sheets-Sheet5 ATTORNEY W. T. POWELL CENTRALIZED TRAFFIC CONTROLLING SYSTEM FORRAILROADS Filed April 13, 1933 April 5, 193-8.

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April 5, 1938. w. T. POWELL 2,113,383

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROAI JS Filed April 15,1935 7 Sheets-Sheet 7 R 5 ATTORNEY 'INVENTO Z0. .7

Patented Apr. 5, 1 938 PATENT OFFICE CENTRALIZED TRAFFIC CONTROLLINGSYSTEM FOR RAILROADS Winfred T. Powell, Rochester, N. Y., assignor toGeneral Railway Signal Company, Rochester, N. Y.

Application April 13, 1933, Serial No. 665,991

25 Claims.

This invention relates to centralized traflic controlling systems forgoverning traffic over railroads and it more particularly pertains tothe communication part of such systems.

In a centralized traffic controlling system of the type contemplated bythe present invention, the switches and signals at various points alonga railroad system are placed under the control of an operator in acentral control ofiice in such a way that the operator may at willchange the position of the switches and signals, subject to thesafeguards which are customarily provided to prevent unsafe operations.Also, the system provides means whereby indications are displayed in thecontrol ofiice to inform the operator of the presence or absence oftrains on the various track sections throughout the territory under hissupervision and to indicate the positions and conditions of the variousswitches, signals and the like.

This invention is particularly useful in such a system which is calledupon to carry out a large number of control and indication functionsduring a short time. A single dispatcher can handle the traffic over alarge section of track, so it is apparent that the controls andindications should be capable of transmission at such a high rate ofspeed that excessive accumulation of stored controls and indications isavoided.

The switches and signals are distributed throughout the territory butthose located relatively near or adjacent each other, together with theapparatus provided for their control are conveniently referred to ascomprising a field station. The communication system is provided tointerconnect the control office with the several field stations and isso organized that the operator obtains complete supervision of thevarious switch and signal devices at the stations.

In accordance with the present invention, the communication systemincludes three line wires extending from the control ofiice through theseveral field stations in series. For convenience in describing theoperation of the system, these three line wires are referred to as theN, A and B lines. Line N is the neutral line over which steppingimpulses and certain control impulses are transmitted. The A and B'linesserve as the return conductors for the N line and are also used fortransmitting certain other control impulses, as well as indicationimpulses. In other words, line N in combination with lines A and Bcomprise the stepping line circuit, while lines A and B in combinationwith line N comprise the message line circuit.

Since the system is of the coded duplex type, it is operable throughcycles for the transmission of controls and/or the transmission ofindications. The system is also of the diplex type which provides forthe transmission of two simultaneous coded control combinations during acycle of operations for selecting two field stations and fortransmitting simultaneous controls t6 these two field stations.

When controls are transmitted to a single station during an operatingcycle, a station selecting code is first applied to the line forselecting the particular station desired, after which the controls aretransmitted to the selected station by means of code impulses. Whencontrols are transmitted to two stations during a single cycle, twostation selecting codes are simultaneously applied to the line forselecting the two particular stations desired, after which the controlsare transmitted to these selected stations by means of simultaneous codeimpulses.

When indications are transmitted, the field station transmitting suchindications first sends a station registering code for registering thatSta-- tion in the control office. ular indications are transmitted fromthe registered station to the control office by means of an additionalcode and are displayed on indicator devices, such as lamps or the likeassociated with the transmitting station.

For the transmission of controls, a predetermined number of impulses ofselected polarities is placed on the stepping line circuit. Theapparatus at the control ofiice and at the field stations operatethrough a cycle of operations, irrespective of the polarities of theimpulses, while the distinctive polarities of such impulses determinethe particular'station to be selected and the controls to be transmittedthereto. During the transmission of a predetermined number of impulsesover the stepping line circuit for selecting a station, an additionalstation may be selected by the distinctive polarities of the impulseswhich are applied to the message line circuit. Inother words, thestepping operation during a cycle is controlled over the stepping lineconductor N with station selection and the transmission of controls toselected stations controlled independ ently over line N and over themessage lines A and B.

If a single station is to be selected which responds to distinctivepolarities applied to the message line circuit, then the impulsesapplied to the stepping line circuit are used for stepping purposes onlyand are all of the same polarity.

Thereafter the partic- If a single station is to be selected whichresponds to a distinctive code applied to the stepping line circuit,then the impulses applied to this circuit control the steppingoperations and by virtue of their polarities, control the selection ofthe desired station. Under this condition, the current impulses appliedto the message line circuit in the control oifice serve no usefulpurpose and are all of the same polarity.

For the transmission of indications, means are provided to condition themessage line circuit during the de-energized periods of the cyclebetween impulses in any one of three different ways. First, leaving theA and B lines closed; second, opening the A and B line circuit once; andthird, opening the A and B line circuit twice. This provides a choice ofthree code characters for each step.

Obviously, the provision of three distinctive code characters for eachstep results in obtaining nine distinctive codes where each completecode comprises two steps. Similarly, twenty-seven distinctive completecodes are obtained where each complete code comprises three steps. Inother words, the number of indication code combinations obtained isequal to three raised to the power of the number of steps.

Other objects and advantages of the present invention will behereinafter set forth in the specification and claims and shown in thedrawings. The characteristic features will be explained more in detailin the following description of one embodiment of the invention, whilevarious other characteristic features and advantages of the system willbe in part pointed out and in part apparent as the descriptionprogresses.

For convenience in describing the operation of the system, the energizedperiods of the stepping line circuit will be referred to as the onperiods while the de-energized periods which separate the on periodswill be referred to as the off periods.

In describing the invention in detail, reference will be made totheaccompanying drawings which illustrate in a diagrammatic manner theapparatus and circuits employed. Those parts having similar features andfunctions are designated in the different figures by like letterreference characters, generally made distinctive either by the use ofdistinctive exponents representative of their location or by the use ofsuitable prefix numerals representative of the order of their operationand in which:-

Fig. 1 is a diagrammatic showing of the threewire line circuit extendingfrom the control ofiice through a typical intervening field station toan end field station;

Fig. 2 illustrates the interlocking circuits of the storing, storingrepeating and code determining relays located in the control office andassoc ated with four field stations;

Figs. 3A, 3B, 4A and 4B illustrate the apparatus and circuits employedat the control ofiice;

Fig. 5 illustrates a portion of the apparatus and circuits employed at atypical even field station;

Fig. 6 illustrates an additional portion of the apparatus and circuitsassociated with the typical even field station illustrated in Fig. 5,together with a small part of the apparatus and circuits employed at atypical odd field station.

In tracing the detailed circuits, Fig. 4A should be placed below Fig.3A, Fig. 4B should be placed below Fig. 3B, and to the right of Fig. 4A,Fig. 6

should be placed below Fig. 5, and Fig. 5 should be placed to the rightof Fig. 3B, with correspondingly numbered lines in alignment.

General description The general plan of operation of the system may bebest understood by referring to Fig. 1, which illustrates thefundamental line circuits extending from the control office through oneintervening field station to the end field station. Two line batteriesare used in the control office for controlling the stepping operationsand for the transmission of controls. Battery NB is convenientlyreferred to as the neutral battery, since it is applied to the neutralline N for impulsing and for transmitting controls to those stationswhich have their controls effected through the medium of the N line.Battery AB is used for transmitting to those stations whose controls areeffected over the A and B line conductors. Battery AB has a center tap Xwhich is connected to line N through battery NB when the system is goingthrough a cycle of operations.

Assuming that relays STR and EPC are picked up and that relays ENC and0C are de-energized, a circuit may be traced for energizing line N whichextends from the terminal of battery NB, front contact 20 of relay STR,front contact 2I of relay EPC, back contact 22 of relay ENC, winding ofrelay IF, back contact 23 of relay EP, N line conductor 24, winding ofrelay IF line conductor 25, winding of relay IF line conductor 26, frontcontacts 21 and 28 of relay SA (relay SA will be picked up as will belater described), to both the A and B line conductors in the directionindicated by the dotted line arrows. The current will divide and partlyreturn by way of the B line conductor 3|, upper winding of relay 2Fconductor 32, upper winding of relay 2F conductor 33, back contact 9 ofrelay 00, upper winding of relay 2F, through the upper portion ofbattery AB to terminal X, back contact 34 of relay ENC, front contact 35of relay EPC, and front contact 36 of relay STR to the terminal ofbattery NB.

Again referring to the end field station, as mentioned above the currentdivides and another portion of the current flows through A lineconductor 3'! in the direction of the dotted line arrows, back contact38 of relay P lower winding of relay 2F conductor 39, back contact 40 ofrelay P lower Winding of relay 2P conductor 4|, back contact I4 of relay0C, lower winding of relay 2F, through the lower portion of battery ABto terminal X and thence to the terminal of battery NB over theremainder of the circuit previously described.

Current in the above assumed direction applied to line N is effective toposition line relays IF, IF and I F to their right hand positions. It isobvious that the reversal of current flow from battery NB, by relay ENCbeing picked up and relay EPC being down, is effective to position linerelays IF, IF and IF to their left hand positions. Therefore, theselective operation of relays EPC and ENC effect the selective operationof the polar relays connected in the neutral line N.

Referring to the dotted line arrows (battery NB current) associated withrelays 2F, 2F and 2F it will be noted that the current flow through thetwo windings of each of these relays is in the same direction. The upperand lower windings of each of these relays are either oppositely woundor the wires leading to the terminals of one winding are reversed withrespect to the wires leading to the other winding, either of whichexpedient results in the 2F relays (with suitable exponent) not beingaffected by the currents above mentioned and being properly operated bycurrent flowing in line conductors A and B in series as will be laterdescribed.

Since the reversal of the current in line N results in a current flow inopposition to that indicated by the dotted line arrows at all points, itwill be apparent that the same relation exists with respect to the 2Frelay windings just mentioned, because the reverse in direction throughone winding of each 2F relay is accompanied by a similar reverse indirection through the other winding of the same relay. BriefiyQline Nmay be impulsed with or impulses from battery NB to effect thepositioning of the IF relays to the right or left respectively, withoutadversely affecting any of the 2F relays.

Referring now to the full line arrows which indicate the current flowwhen the A and B line conductors are energized from battery AB. Thisenergizing circuit may be traced from the terminal of battery AB, lowerwinding of relay 2F, back contact M of relay 0C, conductor 4|, lowerwinding of relay 2F back contact 40 of relay P conductor 39, lowerwinding of relay 2F back contact 38 of relay P conductor 31, frontcontacts 28 and 21 of relay SA conductor 3!, upper winding of relay 2Fconductor 32, upper winding of relay 2F conductor 33, back contact 9 ofrelay OC and upper winding of relay ZF, to the terminal of battery AB;The full line arrows indicate that the current flow through the upperwindings of the 2F relays is in opposition to the current flow throughthe lower windings of these relays and it follows from the abovediscussion relating to the direction of the windings of these relays ortheir terminal connections, that the magnetic flux in the two windingsaid.

It will be assumed that current flowing through the lower windings ofthe 2F relays from left to right and through their upper windings fromright to left, is efiective to position these relays to their right handpositions. By picking up relay 00, the direction of current fiow overthe above described circuit is reversed and since this reversal affectsboth windings of the 2F relays alike, the full line arrows will beassumed transposed to indicate this condition, with the result that bothwindings of the 2F relays are energized in aiding relation, so thatthese relays actuate their contacts to the left hand positions.

A brief statement of the four conditions of energization of the threeline conductors is as follows:

First, line N energized with potential from battery NB, line A energizedwith potential from battery AB and line B energized with potential frombattery AB results in a current flow from battery NB through the IFrelays from left to right. The current from the upper portion of batteryAB through line N is in series aiding relation with the current frombattery NB, while the current flow from the lower portion of battery ABthrough line N is of opposite sign, with the result that the IF relaysare positioned to the right.

Second, reversing the connection of battery NB to line N places batteryNB and the lower portion of battery AB in series aiding relation, whilethe current from the upper portion of battery AB is opposite in signfrom both other battery units,

with the result that the IF relays are positioned to the left.

The third condition is the same as the first with the connection ofbattery AB to lines A and B reversed, which results in the IF relaysbeing positioned to the right because again the'upper portion of batteryAB aids and the lower portion opposes battery NB.

The fourth condition is the same as the second with the connection ofbattery AB to lines A and B reversed, which results in the IF relaysbeing positioned to the left because again the lower portion of batteryAB aids, While the upper portion opposes battery NB.

These four conditions effect the proper operation of the 2F relaysbecause, under the first condition currents from battery NB and theupper portion of battery AB combine and flow through the upper windingsof the 2F relays (on line B) from right to left, which positions theserelays to the right. Under the second condition, currents from batteryN13 and the lower portion of battery AB combine and flow through thelower windings of the 2F relays (on line A) from left to right toposition these relays to the right. Under the third condition, currentsfrom battery NB and the upper portion of battery AB combine and flowthrough the lower windings of the 2F relays (on line A) from right toleft, which positions these relays to the left. Under the fourthcondition, currents from battery NB and the lower portion of battery ABcombine and "flow through the upper windings of the 2F relays (on lineB) from left to right to position these relays to the left.

This discussion relating to the 2F relays does not refer to the 2F relayin the control office, since this is not a polar relay. Under the fourconditions discussed, the currents which combine in a winding of a 2Frelay predominate over the current through the other winding of the samerelay, which is either of comparatively low value or entirelyneutralized by the current fiow from the two battery units inopposition. It is therefore apparent that conditioning the A and B lineconductors by applying and polarities from battery AB thereto'does notinterfere with the conditioning of the N line conductor by battery NB.Further, these two circuits may be simultaneously conditioned withoutinterference, so that controls may be transmitted simultaneously overthe 3 wire circuits indicated in Fig. 1 to two different field stations.

It will be understood that additional stations connected in the line,either between the control ofiilce and the intervening field station orbetween the intervening field station and the end field station, havetheir line circuits arranged the same as the intervening station shownin Fig. 1. As will be more specifically pointed out, the points ofdifference in the circuit connections at different field stations arethe distinctive connections of the code jumpers, which so condition thecircuits that a particular field station will be fully responsive onlyto the particular code assigned to that station.

For the purpose of simplifying the drawings, certain conventionalillustrations have been employed which are used more with the idea ofmaking it easy to understand the principles and mode of operation,rather than with the attempt of illustrating the specific constructionand arrangement of parts and circuits that conventional manner, the useof symbols being employed to indicate the connections to the terminalsof batteries or other sources of current instead of showing all of thewire connections to these terminals.

The symbols and indicate the positive and negative terminalsrespectively of suitable batteries or other sources of current and thecircuits with which these symbols are used always have current flowingin the same direction. The symbols (B+) and (B-) are employed toindicate the positive and negative terminals respectively of a suitablebattery or other source of current having an intermediate tap (CN). andthe circuits with which these symbols are used may have current flowingin one direction or the other, depending upon whether the terminal (B+)or (B) is used in combination with the intermediate tap (CN).

No attempt has been made to show all of the apparatus employed, such asthe total number of manual controls at the control ofiice, the totalamount of equipment or its exact arrangement at the field stations sincethis apparatus and equipment may vary to suit local conditions. Thecharacter of that apparatus illustrated in the typical control officeand at the typical field station will now be considered.

Control o fice equipment-The control oflice includes a control machinehaving a group of control levers for each of the field stations, aminiature track layout corresponding to the actual track layout in thefield and indicating lamps or equivalent devices, together with apparatus and circuits to accomplish the desired operation of the system.That part of the control oflice illustrated in Figs. 3A, 3B, 4A and 4Bshows more particularly that part of a control machine which is typicalof the apparatus associated with a single field station having a trackswitch, a cross-over or the like, together with the general transmittingapparatus employed for all such field stations.

The apparatus for one track switch comprises a miniature track switch2ts, a switch machine control lever 2SML, a self-restoring startingbutton 28B and switch machine indicating lamps NL and RL. Startingbuttons ISB, 38B and 4SB illustrated in Fig. 2 and corresponding switchmachine levers ISML, 3SML and 4SML illustrated in Fig. 4A are associatedwith respective field stations, in addition to the No. 2 field stationapparatus previously mentioned. Attention is particularly directed tothe miniature track switch 215s, starting button 283 and switch machinelever ZSML, because in describing the detailed operation of the systemit will be assumed that station No. 2, which corresponds to thesedevices will be selected and controls transmitted thereto.

Similarly, signal control levers are also associated with the respectiveminiature track switches and starting buttons, but in order to simplifythe drawings and description, these levers have been omitted, since thecontrol of the track switch at station No. 2 may be considered astypical of the control of other types of traflic controlling devices.

The actuation of lever ZSML to one extreme position or the otherfollowed by the actuation of the starting button ZSB, results in thenormal or reverse operation of the track switch corresponding to leverZSML at field station No. 2 illustrated in Fig. 5. The momentaryactuation of a. starting button is stored by its associated storingrelay ISR, 28R, 38R. or ISR, see Fig. 2. Storing repeating relays ISRP,2SRP, 3SRP and 4SRP are associated with corresponding storing relays.Code determining relay [2CD is associated with starting buttons ISB andZSB, while code determining relay 340D is associated with startingbuttons 38B and 4SB. Common relay CM cooperates With the bank ofstoring, storing repeating and code determining relays to deenergize theseries pick-up circuit of the CD relays as long as a CD relay isenergized.

The control oflice includes a biased-to-neutral polar line relay IF anda neutral line repeating relay FP, both of which are normallydeenergized. Slow acting line repeating relays SA and SAP are picked upat the beginning of each cycle and dropped during the change to normalperiod at the end of each cycle. The releasing or drop-away time ofrelay SA is sufficiently long so that its contacts remain in theiractuated positions during all off periods between successive on periods.During the last 0115 period, which is comparatively long for the purposeof returning the system to normal, relay SA is released and after apredetermined interval of time, its repeating relay SAP is released.

Associated with line relay F and its repeating relays is a bank ofstepping relays IV, 2V and 3V,

together with a half step relay VP, which are provided to mark ofi thesuccessive steps of each cycle. An impulsing relay E is jointlycontrolled by the half step relay and the stepping relays, with theoperations of relay E repeated by impulse repeating relay EP, which inturn opens and closes the N line conductor. Relays E and EP also controlthe pick-up and stick circuits of the indication message relays IM, 2Mand 3M, as well as controlling the indication executing circuits, all ofwhich will be specifically pointed out in the detailed description. Linerelay 2F, of the neutral type, is for the purpose of controlling thecircuits to the message relays IM, 2M and 3M and also to start thesystem into a cycle of operations in response to a change in conditionat a field station.

The polarities of the impulses applied to the stepping line circuit frombattery NB on successive steps of a cycle, are determined by positivecode sending relay EPC and negative code sending relay ENC. Thereference character E associated with these code sending relaysindicates that even numbered stations are selected over the line circuitcontrolled by these two relays. This is merely a typical arrangementused for convenience in describing the operation of the system, sincethe stations controlled over line N could as well be referred to as oddstations. The polarities of the impulses applied to the message linecircuit from battery AB are determined by odd code sending relay OC andfor convenience in the description, it will be assumed that odd numberedstations in the system are controlled over the message line circuit.

A starting relay STR is picked up to initiate a cycle of operations,both when controls are to be transmitted to an odd and/or an evenstation due to the manual initiation of the cycle in the control ofliceand when indications are to be transmitted due to the automaticinitiation of a cycle by a field station. Field start relay FC is pickedup when the cycle of operations is initiated by a field station andoflice start relay C is picked up when a cycle of operations isinitiated in the control office.

in Fig. 4A. Pilot relays IPT and ZPT are selectively connected to theindication buses so that they may be positioned on the first step of thecycle when indications are transmitted. Similarly, additional pilotrelays (not shown) may be provided for additional steps, up to the pointwhere a sufficient number of codes for station registration is obtained.

Station relays IST and 2ST are provided for registering, in the controloffice, the station transmitting indications. The conductor indicatedindication phantom is not used in this embodiment for connection to astation relay, because when controls aloneare transmitted during acycle, the system inherently transmits back to the control ofilce anindication code combination which positions relays IPT and 2PT to theleft and which code combination does not correspond to a field station.

A choice of three code characters for each. step results in selectivelypositioning the two pilot relays in three distinctive positions, two ofwhich may be used as indicated. By adding two more pilot relays andconditioning them on the second step, nine different code combinationsare obtained, eight of which may be used, with the ninth or phantomcombination not being employed.

The control machine also includes suitable indication storing relays HRand ZIR. for storing the indications of whether the associated trackswitch is in its locked normal position, its locked reverse position, orunlocked, as repeated by a switch repeating relay at the station.Indicator lamp NL is displayed to indicate the locked normal positionand indicator lamp BL is lighted toindicate the locked reverse position.Both of these lamps unilluminated is an indication that the switch is inits unlocked position.

It will be obvious that additional indication receiving relays may beprovided and connected in the manner typically illustrated by relays IIRand 21R, for receiving and displaying additional indications from aregistered field station.

Field station equipment.-The even field sta tion illustrated in Figs. 5and 6 is typical of all field stations of the system and may be adaptedto be used at the first, second or any other location by merely alteringcertain code jumpers to arrange for the desired codes and by alteringcertain wire connections to arrange for the distinction between odd andeven stations. The end field station differs slightly from the otherswith respect to contacts 21 and 28 on relay SA. and resistance 313. thepurpose of which will be pointed out later in the description. Forconvenience in the description, the field station illustrated in Fig. 5and in the portion below the dashed line in Fig. 6, is assumed to beeven station No. 2. It will be understood that the equipment andapparatus at all other even field stations are the same as illustratedin connection with the No. 2 station with the exception of the abovementioned code jumpers.

All odd numbered stations, of which station No. l partly illustratedabove the dashed line of Fig. 6 is typical, have apparatus and circuitsthe same as the illustrated even field station, except that the polarcontact I86 of relay 2P is used at the odd stations and is not used atthe even stations. Likewise, polar contacts similar to E9! of relay IFare not used on corresponding relays at the odd stations. Theorganization of the different odd station circuits is otherwise the sameexcept for the distinctive connections of the code jumpers.

With reference to Fig. 5, a turn-out track is illustrated as connectedto a main track by means of a track switch T8 which is operated from oneextreme locked position to the other by a suitable switch machine SW.The switch machine is operated by the two-position polar magnetic stickrelay SMR which is in turn controlled from the control ofilce throughthe medium of the com-' munication system.

Suitable signals are associated with the track switch T8 for governingtrafiic thereover and automatic signaling means are provided,interrelating the trafiic over this track switch with such othersections of track and traffic controlling devices as may be associatedtherewith. These signals are also controlled from the control officethrough the medium of the communication system by means of controlrelays operated in a manner similar to the operation of relay SMRF,which operation may be considered typical. For the sake of simplicity,the signals and signal relays are omitted from the present disclosure.The detector track section having a normally closed track circuit withthe usual track relay and suitable track battery (not shown), are alsoassociated with the track switch T3 for indicating the passage of trainsthereover.

Switch repeating relay WP shown in Fig. 6 repeats the position andcondition of track switch TS This relay is of the polar neutral type andis so controlled that it positions its polar contact I98 to the rightwhen the track switch is in its normal locked position and to the leftwhen the track switch is in the reverse locked position. Neutralcontacts 200 and 2M are dropped when the track switch is in its unlockedor mid stroke position. It will later be explained how these threeconditions of relay WP effect the transmission of indications from thisstation when it is registered in the control office. It is believed thatthis explanation will be sufficient to indicate the manner in whichsimilar indications relating to other conditions at the field stationmay be transmitted, as will be apparent from a discussion of the typicaloperations effected by the positions of relay WP A quick actingbiased-to-neutral polar relay IF repeats the impulses applied to line N.A quick acting biased-to-neutral polar relay ZF responds to the impulsesapplied to line conductor A. As above mentioned, the polar contacts onthis relay are not used at even numbered stations but to make the systemsymmetrical, it is preferred to make use of the windings of this relayat all field stations. A quick acting line repeating relay FP repeatsthe energizations and deenergizations of the N line circuit,irrespective of the polarities-pf the energizations. A slow acting relaySA of the neutral type repeats the energized condition of relay F'P andis used to define the bounds of each cycle of operations at the fieldstation, since it is energized at the beginning of each cycle and is notdropped until the change to normal period at the end of the cycle.

A bank of stepping relays IV 2V 3V and the associated half step relay VPis likewise included at each field station. Since these relays operatein a similar manner and in synchronism with the stepping relay bank inthe control ofiice, their detailed circuits have not been shown.Conductors 150, WI, [52, I53 and I54 leading to bracket BK correspond toconductors 50, 52, 53 and 54 of Fig. 3B so that it is obvious how thefield station stepping relay bank operates in synchronism with thecontrol ofiice bank of stepping relays. Odd station stepping relays IV2V and 3V shown in the upper portion of Fig. 6 are illustrated for thepurpose of indicating the manner in which the 2F relays efiect stationselection and control relay operation at odd numbered sta- .tions.

For the purpose of illustrating the selection of a station, stationrelay S0 is provided. These station relays are picked up at all stationsat the beginning of a cycle and as stepping progresses, they are droppedout, one-half of those up being dropped at each step, until only the oneassociated with the desired station remains picked up after the stationselecting steps have been marked off. It is to be understood that anysuitable station selecting means may be employed, such as the use ofpilot relays and a station relay at each station and still be within thescope of the present invention.

A lock-out relay L0 is provided at each station to determine when aparticular station is to transmit new indications. Relay L0 is picked upduring the initiating period of a cycle when indications are transmittedand is stuck up until the change to normal period at the end of a cycle.Resistance units such as 2R are provided to compensate for theresistance of the 2F relays in the A line conductor toward the end ofthe line, which is removed from this conductor when the lock-out relayis energized. Resistance 3R at the end field station is for the purposeof providing a return path to line B when line N is energized during theconditioning period of a control cycle.

Line impulsing relays P IP and 2P are provided to impulse the A and Bline circuit to provide code combinations during the transmission ofindications. These relays are conditioned in accordance with thecondition of the No. 1 pulse bus and the No. 2 pulse bus as selected bythe code jumpers and relay contacts at the different steps of a cycle.Relay P also functions to effect the look-out circuit operation at thebeginning of a cycle, in response to a change in condition at thestation as repeated and stored by change storing relay CHS It isbelieved that the nature of the invention, its advantages andcharacteristic features may be best understood with further descriptionbeing set forth in the manner of operation.

Detailed operation Normal at-rest condition.Although the system may beinitiated from the field stations, the line circuits are normallydeenergized and similarly, the remaining circuits of the system arenormally deenergized, with a few exceptions. For example, relay WP shownin Fig. 6 is normally energized over a circuit which is controlled bythe switch machine and associated apparatus, in a manner which iswell-known in the art. The track circuit is preferably of the closedcircuit type, so that a normally energized track relay (not shown) isprovided to repeat the unoccupied and occupied conditions of the tracksection. Likewise, one or more normally energized relays control thestick circuit of a normally energized change relay, in such a Way that achange in condition at a field station drops the change relay, which inturn picks up the change storing relay CHS Since these circuitarrangements ISB is actuated, a circuit is closed for picking up relayISR extending from contact 42 of button I SB, back contact 43 of relayISRP and Winding of relay ISR, to Relay ISR closes a stick circuit foritself extending from front contact 44 of relay ISR and back contact 243 of relay ISRP to the winding of relay ISR.

If button 2SB is actuated, a circuit is closed for picking up relay 2SRextending from contact 45 of button 2SB, back contact 46 of relay ZSRPand winding of relay 28R, to J Relay 2SR closes a stick circuit foritself extending from front contact 41 of relay 2SR and back contact 46of relay 2SRP to the winding of relay 2SR. If button 383 is actuated, acircuit is closed for picking up relay 3SR which extends from contact 48of button 383, back contact 49 of relay 3SRP and winding of relay 3SR,to Relay 3SR closes an obvious stick circuit for itself by way of itsfront contact 55. If button 4SB is actuated, relay 4SR is picked up overa circuit extending from contact 56 of button 4SB and back contact 51 ofrelay 4SRP to the winding of relay 4SR. Relay 4SR closes an obviousstick circuit for itself by way of its front contact 58.

The picking up of relay ISR closes a circuit for picking up relay I SRPwhich extends from back contact 59 of relay SAP, front contact 6''! ofrelay lSR, back contact BI and winding of relay ISRP, to The picking upof relay 28R closes a circuit for picking up relay 2SRP extending fromback contact 59 of relay SAP, front contact 62 of relay 2SR, backcontact 63 and winding of relay 2SRP, to Stick circuits for relays ISRPand ZSRP are established through their make-before-break front contacts6i and 63 respectively to at back contact 64 of relay I2CD.

The picking up of relay. 3SR closes a circuit for picking up relay 3SRPwhich extends from back contact 59 of relay SAP, front contact 65 ofrelay 3SR, back contact 66 and winding of relay 3SRP, to The picking upof relay 48R closes a circuit for picking up relay 4SRP which extendsfrom back contact 59 of relay SAP, front contact 67 of relay 4SR, backcontact 68 and winding of relay 4SRP, to Stick circuits for relays 3SRPand 4SRP are established through their make-before-break front contacts66 and 68 respectively to at back contact 69 of relay 340D. The pickingup of the storing repeating relays ISRP, ZSRP, 3SRP and 4SRP causes thedropping of the associated storing relays by opening back contacts 43,46, 49 and 57.

The actuation of one or more of the starting buttons during a cycleresults in the corresponding storing relay or relays being picked up andstuck up. Then when the system returns to normal, the correspondingstoring repeating relay or relays will pick up, stick and cause therelease of the associated storing relay or relays.

The stations are arranged in pairs, with each code determining relaycontrolling the selection of one odd and one even station and thetransmission of controls thereto. As a typical example, when relay I2CDis up and both relays ISRP and 2SRP are up during a cycle, odd station(No. 1) and even station (No. 2) are selected and controls transmittedto both stations during the same cycle. With relay IZCD up and relaylSRP up during a cycle, odd station No. 1 alone is selected and controlsare transmitted to it alone. Similarly, when relays IZCD and ZSRP are uptogether during a cycle, station No. 2 alone is selected and thetransmission of controls tothis station alone is effected. Thisdiscussion applies to relays 340D, 3SR-P and 4SRP which govern thetransmission of controls to another pair of stations, No. 3 and No. 4.

The picking up of relay ISRP closes a circuit for picking up relay IZCDwhich extends from back contact 8| of relay SAP, back contact iii ofrelay CM, conductor l9, front contact 1" of relay ISRP, back contact 12and winding of relay lZCD, to When relay 2SRP is picked up alone, thenthe circuit for picking up relay ltZCD extends from back contact 8| ofrelay SAP, back contact 10 of relay CM, back contact ll of relay ISRP,front contact 13 of relay ZSRP, back contact 12 and winding of relayIZCD, to If both relays ISRP and ZSRP are up, the circuit previouslydescribed through front con tact H of relay ISRP is effective to pick uprelay l'lCD. The picking up of relay lZCD closes a stick circuit foritself which extends from winding of relay CM, front contact 14 of relaySRP or front contact 15 of relay 2SRP (or both), front contact 12 andwinding of relay IZCD, to

The picking up of relay 3SRP closes a circu for picking up relay 340Dwhich extends from back contacts 8!, 10, H and 13 of relays SAP. CM,ISRP and ZSRP respectively, conductor l8, front contact i6 of relay3SRP, back contact l! and winding of relay 34CD, to The picking up ofrelay ASRP closes a similar circuit for picking up relay 34CD, thiscircuit extendin through back contact 16 of relay SSRP and front contact18 of relay 4SRP. The picking up f relay SACD closes a stick circuit foritself extend ing from winding of relay CM. one, th' other or both frontcontacts I9 and of relays SSRP and GSRP respectively and front contactll of relay 340D to the winding of this relay.

The stick circuits of all code determining relays includes the windingof relay CM, which picks up and removes the potential from conductor 19so no other CD relay can pick up until th one that is up is deenergized.It is obvious tha in the event of two or more odd or two or more evenstoring repeating relays being up at the same time with the system inits normal period the corresponding CD relay nearest the p tential atback contact H! of relay CM will ha preference. because the extendedpick-up wire I to other CD relays to the right is de-energized.

The picking up of relay IZCD transfers (at its make-before-break contact64) the stick circuit for relays lSRP and ZSRP to at back contact 8! ofrelay SAP and at front contact 8-? relay SA. Relays SA and SAP pick upin sequence during the conditioning period at the start of a cycle andare dropped in sequence at the end of a cycle, so that the stick circuitfor relays I (with the corresponding CD relay picked up) have beenreleased. Those storing repeating relays (if any) which are stuck up atthis time to at a back contact such as 64, 69 or the like of theirassociated CD relays are not released, so that another CD relay has achance to be picked up to start another cycle when the previouslyenergized CD relay is deenergized to deenergize and release relay CM bythe dropping of the corresponding storing repeating relay or relays.

Briefly stated, as many storing relays may be picked up as there arestarting buttons actuated, irrespective of the condition of the system.An exception to'this is that a storing relay such as relay ISR; cannotbe picked up when relay ISRP is up, because back contact 43 is open.There is no need of operating relay ISR under this condition, becauseits associated station is either already being selected or a storedcondition for this station is waiting. As many storing repeating relaysmay be picked up when the system is in its normal period as there'arestoring relays up, after which the corresponding storing relays aredropped. Only one code determining relay can be up at the same time andcontrols will be transmitted to the odd, or even, or both stationsassociated with this code determining relay, as determined by the pickedup condition of the odd, or even, or both storing repeating relays.

It is obvious that after a cycle of operations has been started as aresult of the picking up of one storing repeating relay, the otherstoring repeating relay of the pair must be prevented from picking up.Otherwise, a storing repeating relay picking up after the start of acycle when its associated CD relay is up, would not be up in time totransmit all of the codes necessary. Therefore, when relay SAP picks upto start a cycle, the removal of potential from conductor 83 at its backcontact 59 prevents the picking up of any storing repeating relay. It isunderstood that under this condition, the storing relay is stuck upuntil the end of the cycle, at which time the corresponding storingrepeating relay can be picked up and stuck up until the end of the nextcycle.

It will now be assumed that the operator in the control office desiresto transmit controls to station No. 2 illustrated in Figs. 5 and 6. Whenstarting button 2SB is actuated, relays ZSR, 2SRP and I2CD are picked upas above described. A circuit is now closed for picking up relay C whichextends from back contact 84 of relay SA, conductor ll, back contact 85of relay ENC, front contact 86 of relay I2CD and winding of relay C, toRelay C closes a stick circuit for itself by way of its front contact 81to at back contact 88 of relay SAP, which iseffective until relay SApicks up and thereafter the stick circuit extends to at front contact 84of relay SA.

The operation of relay C opens the pick-up circuit of relay FC at backcontact 89, which prevents the picking up of relay FC after the cycle isinitiated by a manual start in the control ofilce. The picking up ofrelay C closes a circuit for picking up start relay STR which extendsfrom front contact 90 of relay C and winding of relay STR, to A circuitis now closed for picking up relay EPC which extends from front contact9| of relay ZSRP, front contact 92 of relay lZCD, even control conductor93, back contacts 94, 95 and 96 of relays 3V, 2V and 'IV respectively,conductor l0, front contact 91 of relay C and winding of relay EPC, toThis marks the beginning of the conditioning period by applyingpotential to line N for the purpose of conditioning the relays at thefield stations. Relays IF, IF (and similar line relays at all thestations) are now positioned to the right by means of a circuitextending from the terminal of battery NB, front contact 26 of relaySTR, front contact 2| of relay EPC, back contact 22 of relay ENC,conductor I3, Winding of relay IF, back contact 23 of relay EP, N lineconductor 24,.winding of relay IF, resistance 3R at the end station,upper winding of relay 2F B line conductor 33, back contact 9 of relay00, upper winding of relay 2F, through the upper portion of battery AB,back contact 34 of relay ENC, front contact 35 of relay EPO and frontcontact 36 of relay STR to the terminal of battery NIB. Current flow inthis circuit includes the upper portion of battery AB which aids batteryNB and is effective to position the 2F relays at all stations to theright and to energize the 2F relay in the control office. A circuit isnow closed for picking up relay FP in the control office which extendsfrom polar contact 99 of relay IF in its right hand dotted position andwinding of relay FP, to Relay FP closes a circuit for picking up relaySA which extends from front contact I00 of relay FF and winding of relaySA, to A circuit is closed for picking up relay SAP which extends fromfront contact IUI of relay SA and winding of relay SAP, to

Relay FP (Fig. 5) is picked up over a circuit extending from contact 202of relay IF in its right hand dotted position and winding of relay FP toA circuit is closed for picking up relay SA which extends from frontcontact 203 of relay FF and winding of relay 8A to Before the picking upof relay SA relay S0 is picked up over a circuit extending from backcontact 294 of relay SA conductor 299 back contacts 205, 206 and 291 ofrelays 3V 2V and IV in series, control bus contact I91 of relay IF inits right hand dotted position and winding of relay S0 to Relay SOestablishes a stick circuit for itself over the circuit just described,to at its front contact 208 which is effective after relay SA picks up.

It is to be understood that relays similar to- IF FP SA and S0 at allother even field stations are operated by means of circuits similar tothose just described. At all odd field stations, the SO relays arepicked up over a circuit similar to that which extends from applied toconductor 299 (Fig. 6), from back contacts similar to 294 of relayssimilar to SA and thence through back contacts 29I, 292 and 293 ofrelays 3V 2V and IV respectively, control bus contact I96 of relay 2F inits right hand dotted position and the winding of the SO relay which isconnected to conductor 294.

Referring back to the control oflice, the picking up of relay SAP closesa circuit for picking up relay EP which extends from front contact 29 ofrelay SAP, back contact 39 of relay E and lower winding of relay EP, toThe picking up of relay EP deenergizes line N at back contact 23, tomark the end of the conditioning on period and the beginning of thefirst off period.

Relay 8A at the end field station is picked up by means of a circuitsimilar to that described for picking up relay SA and by closing itsfront contacts 21 and 28, the continuity of the A--B line circuit isestablished (see Fig. 1). This is effective to energize the A and Blines with potential from battery AB applied to the A line conductor,which maintains the 2F relays (with suitable exponents) positioned tothe right.

During this cycle, since it is assumed that a single even station is tobe selected, the condition of the A and B line conductors is not changedbut these conductors are maintained energized in the same direction sothat the 2F relays (with suitable exponents) remain actuated to theirright hand positions. Since back contact I02 of relay 2F in the controlofiice is maintained open, the pick-up circuits of relays IM,

2M and 3M are not energized during this cycle. Therefore, (B-) potentialis applied to pilot relays IPT and 2PT, over circuits which will belater described, so that these relays are both positioned to the left toselect the indication phantom wire.

In the event that starting button 4SB is actuated, relays ISR, 4SRP and340D are picked up as above described. Since this requires the selectionof an even station, the operations are the same for conditioning theline circuits as explained in connection with relay I2CD, except thatthe circuit for energizing the even control bus 93 which picks up relayEPC now extends through front contact 4SRP and front contact I04 ofrelay 34CD. Also the pick-up circuit for relay C extends through frontcontact I05 of relay 340D instead of front contact 86 of relay I2CD. Itwill thus be seen that the picking up of any CD relay initiates a lcontrol cycle by applying potential to line N during the conditioningperiod. As will be later explained, the different conditions set up bythe different CD relays which are picked up result in distinctiveimpulses being applied to the line circuits, following the conditioningimpulse, as controlled by the jumper and lever connections associatedwith the one particular CD relay which is picked up during the cycle.

In the event that starting button ISB is actuated, relays I SR, ISRP andI2CD are picked up and the line is conditioned as above described inconnection with the operation of button 28B, except that relay EPC isenergized by means of a circuit extending from front contact ID! ofrelay ISRP, front contact I08 of relay I2CD, odd control bus I 96, backcontacts I09, III) and III of relays 3V, 2V and IV respectively,conductor I0, front contact 91 of relay C and winding of relay EPC, to

In the event that button 38B is actuated, relays 3SR, BSRP- and 34GBpick up as above explained and the N line circuit is conditioned in thesame manner as described in connection with the actuation of button 2SB,except in this case relay EPC is energized over the circuit justdescribed, including odd control bus I96, but this time through frontcontacts I I2 and I I3 of relays 3SRP and 340D respectively.

Polarity selection of impulses.It will first be assumed (and laterdescribed) that the stepping relays in the control office and at thefield stations step through the cycle in synchronism (except certainfield stations which are dropped out during the cycle). When line N isdeenergized to mark the end of the conditioning period as previouslydiscussed, relay IF in the control office, relay I F at the fieldstation illustrated in Fig. 5 and similar line relays at all other fieldstations are deenergized. The first stepping relay I03 of relay in thecontrol office is now picked up, following which relay E picks up andrelay EP drops to mark the end of the first off period.

The picking up of relay IV establishes the No. 1 control conditioningcircuit, extending from front contact 9| of relay 2SRP, front contact 92of relay I2CD, conductor 93, back contacts 54 and 95 of relays 3V and 2Vrespectively, front contact 95 of relay IV, No. 1 even conductor H6,front contact I I4 of relay I 2CD, jumper 254, EPC bus II5, frontcontact 98 of relay C and winding of relay EPC, to This circuit iseffective to pick up relay EPC during the first o period for energizingline N with potential during the following or first on period.

In the event that jumper 254 is connected to ENC bus II'I instead of EPCbus I I5, then the above described circuit extends by way of bus I I1and the winding of relay ENC, to which is effective to pick up relay ENCfor energizing line N with potential during the first on period.

Relay 2V is picked up during the second "off period and the No. 2 evenconductor H8 is selected at front contact 95 of relay 2V. The circui textends through front contact 9 of relay I2CD and jumper 255' to the ENCbus II I which is effective to energize relay ENC for selecting apotential to be applied to line N during the second on period. In theevent that jumper 255 is connected in its alternate position to EPC busII5, then relay EPC is picked up to select potential for the No. 2 onimpulse.

Relay 3V is picked up during the third off period to select the No. 3even conductor I20 by way of its front contact 94. This circuit isextended through front contact I2I of relay I2CD to lever ZSML. Shouldlever 2SML be in its right hand position, the conditioning circuit wouldbe connected to the EPC bus H5 for picking up relay EPC to applypotential to line N during the third on period. Or if lever ZSML is inits left hand dotted position, the ENC bus I I I is selected and relayENC is picked up to apply potential to line N during the third onperiod.

From the above discussion, it will be apparent that line N is impulsedwith a combination (following the conditioning impulse) of impulses withjumpers 254 and 255 and lever ZSML in the positions indicated in thedrawings. Also, the polarity tobe applied to line N during an on periodis determined by the particular polarity control relay EPC or ENC whichis picked up during the preceding off period. In the event that relay340D is picked up as a result of button 483 being actuated, then theimpulses applied to line N are The first impulse (following theconditioning impulse) is as determined by jumper 256 connecting the No.1 even conductor I I6 by way of front contact I22 of relay 340D to theENC bus. The second impulse is as selected by jumper 251 connecting theNo. 2 even conductor H8 by way of front contact I23 of relay 34CD to theEPC bus. The third impulse is as determined by lever 4SML connecting theEPC bus to the No. 3 evenconductor I20by way of front contact I24 ofrelay 34CD.

In the event that relay |2CD is picked up as a result of button ISBbeing actuated, the AB line circuit is impulsed (following theconditioning impulse) with a combination of impulses. The first impulseis because juniper 250 is connected to 00 bus I25 for completing anenergizing circuit for relay 0C when relay IV is picked up, whichextends from front contact II" of relay ISRP, front contact Hi8 of relayI2CD, odd control conductor I06, back contacts I09 and H0 of relays 3Vand 2V respectively, front contact III of relay IV, No. 1 odd conductorI26, front contact I21 of relay I2CD, jumper 250, conductor I25, windingof relay 0C and front contact II of relay C, to Relay 00 connectspotential from battery AB through the lower winding of relay 2F andfront contact 9 of relay O0 to B line conductor 83, while potential frombattery AB through the upper winding of relay 2F is connected to the Aline conductor M at front contact I4 of relay 0C.

The second impulse is because jumper 25I- is effective to deenergizerelay 00 when the No. 2 odd conductor I28 is selected at front contactHII of relay 2V, which conductor extends through front contact I29 ofrelay I2CD to jumper 251. Relay 00 remaining deenergized reverses theconnection of battery AB to lines A and B from that explained inconnection with the first impulse. The third impulse is because withlever ISML in the position shown, relay 0C is deenergized when thecircuit including the No. 3 odd conductor I and front contact I3I ofrelay I2CD is established.

Jumpers 252, 253 and lever 3SML are selected by relays 3SRP and 34GB andwhen connected as shown, result in relay 00 being picked up during theNo. 1 and the No. 2 odd steps respectively, to make the first twoimpulses in the A line This is because these two jumpers are connectedby way of front contacts I32 and I33 of relay 340D and the No. 1 odd andNo. 2 odd conductors to the odd control conductor I06 by way of frontcontacts III of relay IV and III) of relay 2V respectively, at the firsttwo steps of the cycle. Odd control conductor I06 extends through frontcontact I I3 of relay 340D and front contact N2 of relay 3SRP, to Lever3SML de-energizes the 00 bus I25, as selected on the third step by wayof front contact I34 of relay 340D.

From the above description it will be seen that line circuits N and ABare distinctively conditinned with and impulses, as selected by acombination of SRP and CD relays. In other words, a CD relay beingpicked up in combination with an even numbered SRP relay, causes line Nto be impulsed with a combination of and impulses as determined by theassociated jumper and lever connections. A CD relay being up incombination with an odd numbered SRP relay causes the A and B linecircuit to'be impulsed with a combination of and impulses as determinedby the associated jumper and lever connections. Since these two linecircuits are independently energized without interference between thetwo circuits, it is apparent that the system will function to transmit asingle combination of impulses for selecting a single odd or evenstation, or a double combination of impulses for selecting an odd and aneven station during the same cycle.

Line impulsing and operation of stepping relay ban7c.-Relay IV in thecontrol ofiice is picked up during the first off period as a result ofrelay IF being de-energized to drop relay FP. The circuit for picking uprelay IV extends from front contact I 35 of relay SA, back contact I36of relay FP, back contact I31 of relay VP, back contact I-3B of relay 2Vand winding of' relay IV, to

(). Relay IV closes a stick circuit for itself extending from frontcontact I of relay SA, front contact I39 and winding of relay IV, toRelay E is now picked up over a circuit extending from back contact I40of relay 3V, back contact I4I of relay 2V, front contact I42 of relayIV, back contact I43 of relay VP and winding of relay E, to

Relay EP is now dropped due to the energizing circuit through its lowerwinding being open at back contact 30 of relay E. Relay EP is slightlyslow to release due to its upper winding being short circuited at itsfront contact I44. This slow releasing feature of relay EP is for thepurpose of timing the off periods between impulses. The slight delay inthe release of relay EP delays the energization of the line. The releaseof relay EP and the resulting energization of line N at back contact 23marks the end of the first off period and the beginning of the first onperiod.

Relays IF and FF now pick up in turn and relay FP closes a circuit forpicking up relay VP extending from front contact I 45 of relay SA, frontcontact I46 of relay F'P, back contacts I41 and I 48 of relays 3V and 2Vrespectively, front contact I49 of relay IV and winding of relay VP, toRelay VP establishes a stick circuit for itself extending from frontcontact I45 of relay SA, front contact I60 of relay VP and over theremainder of the previously described circuit to the winding of relayVP. The stick circuit is effective until stepping relay 2V picks up andopens its back contact I48, which occurs during the second off period.For maintaining relay VP in its energized condition during the secondoff period, an additional stick circuit is established which extendsfrom front contact I45 of relay SA, back contact I46 of relay FP, frontcontact I6I and winding of relay VP, to

Relay VP, in picking, up opens the circuit of relay E at back contactI43, so that relay E drops after a predetermined time interval andcloses the pick-up circuit for relay EP at its back contact 30. Relay EPpicks up and deenergizes line N by opening its back contact 23 to markthe end of the first on period and the beginning of the second offperiod.

Relays IF and FF are now dropped and relay 2V is picked up over acircuit extending from front contact I35 of relay SA, back contact I36of relay FP, front contact I3! of relay VP, back contact I62 of relay3V, front contact I63 of relay IV and winding of relay 2V, to Relay 2Vestablishes an obvious stick circuit for itself by way of its frontcontact I64.

Relay E is now picked up over the previously described circuit throughback contact I40 of relay 3V, which now extends through front contactsMI and I43 of relays: 2V and VP respectively. Relay EP is dropped andline N is energized as before, which marks the end of the second offperiod and the beginning of the second on period.

Relays IF and PP are now picked up in turn and relay VP is dropped,because one stick circuit is open at back contact I48 of relay 2V andthe other stick circuit is open at back contact I46 of relay FP. Relay Eis now dropped because its energizing circuit is open at front contactI43 of relay VP. Relay EP is again energized and line N is deenergizedto mark the end of the second on period and the beginning of the thirdoff period.

Relays IF and FF are now dropped and relay 3V is picked up over thepreviously described circuit, which now extends through back contact I31of relay VP and front contact I38 of relay 2V to the Winding of relay3V. Relay 3V closes an obvious stick circuit for itself by way of itsfront contact I65. Relay E is now picked up over a circuit extendingfrom front contact I40 of relay 3V, back contact I43 of relay VP andwinding of relay E, to Relay EP is now dropped to mark the end of thethird off period and the beginning of the third "on period, byenergizing line N.

Relays IF and FP now pick up in turn and relay VP is picked up over thepreviously described circuit which now extends through front contact I41of relay 3V. Relay VP closes the previously described stick circuits foritself through its front contacts I60 and I6I. Relay E is now releasedbecause the potential applied to its winding through front contact I 40of relay 3V is interrupted at back contact I43 of relay VP. Relay EP ispicked up as before and line N is deenergized to mark the end of thethird on period and the beginning of the change to normal period.

Relays IF and PP now drop in turn and since there is no other steppingrelay to be picked up, relay VP remains stuck up and relay E cannotagain pick up to deenergize relay EP. After a predetermined interval oftime, relay SA is dropped because its energizing circuit remains open atfront contact I00 of relay FP. Relay SAP is dropped after an additionalinterval of time because its energizing circuit remains open at frontcontact IOI of relay SA. The dropping of relay SA deenergizes thepick-up and stick circuits of the stepping relays and the half steprelay, by opening its front contacts I35 and I45, with the result thatthese relays are dropped.

Relay 2SRP is dropped when relay SA drops its front contact 82. Theenergizing circuit of relay I 2CD is opened at front contact "I5 ofrelay 2SRP, with the result that relays IZCD and CM are dropped. Relay Cis deenergized when relay SA drops its front contact 84 and since relayI2CD is dropped at substantially the same time, the pick-up circuit ofrelay C through front contact 86 of relay IZCD is interrupted. Relay STRis deenergized when relay C drops its front contact 90. Relay EP isdeenergized when relay SAP drops its front contact 29.

Since relays IF and FP operate substantially in synchronism with thecorresponding relays in the control oflice and since the stepping relaysillustrated in Figs. 5 and 6 operate substantially in synchronism withthe stepping relays in the control office, it is not believed necessaryto explain the field station stepping operations in detail. It should bementioned, however, that the SA relays at the field stations are droppedsubstantially in synchronism with the corresponding relay in the controloflice and when relay 8A at the end station is released, the AB linecircuit is deenergized which results in deenergizing relay 2F in thecontrol ofiice and the 2F relays at the field stations. The system isnow in its normal condition.

Station selection and transmission of controZs.It will now be assumedthat the stepping relays in the control oiiice and at the field stationoperate as above described and an explanation will be given of thecircuits which are efiective during this operation for selecting theillustrated even station and the transmission of controls thereto.

As above explained, line N is conditioned with ill;

a impulse for picking up the station relays similar to relay S at allfield stations. During each off period of the cycle, all SO relays whichremain up throughout the preceding on period are stuck up by means of acircuit similar to that extending from front contact 208 of relay S0front contact 204 of relay SA back contact 2I2 of relay FF (and contactI91 of relay IF in its neutral position in multiple) and winding ofrelay S0 to With jumpers 2I0 and 2 connected as shown in Fig. 5, the No.2 even station is selected when starting button 2SB in the ofiice isactuated. It will be recalled that the actuation of this button causesrelays 28R? and I2CD to be up during the cycle and that these two relaysup together energize even control bus 93. This energized bus is extendedto relays EPC and ENC in sequence on the first two steps, by way ofjumpers 254 and 255 so that line N is impulsed for station selection.

Relay IF at the illustrated station (and similar relays at all otherstations) is positioned to the right by the impulse. A circuit is closedfor energizing relay SO which extends from front contact 208 of relay S0back contacts 205 and 206 of relays 3V and 2V respectively, frontcontact 207 of relay IV jumper 2l0, control bus contact I91 of relay IFin its right hand dotted position, terminal I and winding of relay SO toAt those stations having a jumper similar to 2 I 0 connected to thecontrol bus, relays similar to so will be maintained energized duringthe first on period by means of a circuit similar to that justdescribed. At those stations not having a code jumper similar to M0connected to the control bus, the SO relays will be dropped becausethere is no circuit for maintaining them energized.

When the system advances into the second off period, relay SO andsimilar relays at other stations, which are up will be stuck up aspreviously described. It is obvious that the stick circuits of thosestation relays similar to relay SO which were dropped during the first"on period, are not completed during the second off period since theircontacts similar to 208 are open.

The system advances into the second on period after relay 2V has beenpicked up and the impulse applied to line N is effective to positionrelay IF (and similar relays at all other stations) to the left. Acircuit is completed for energizing relay SO extending from frontcontact 208 of relay S0 back contact 205 of relay 3V front contact 205of relay 2V jumper 2H, control bus contact I91 of relay IF in its lefthand dotted position, terminal I10 and winding of relay S0, to Any otherstation with a jumper connection similar to 2| I and with its SO relayup, will maintain this relay energized throughout the second on periodin a similar manner. Any other station with its SO relay up and withoutsuch a jumper connection will drop this relay in the second on period.

During the third off period, relay 3V is picked up and relay S0 is stuckup over a circuit extending from front contact 208 of relay S0 frontcontact 205 of relay 3V and winding of relay S0 to This maintains relaySO picked up during the remainder of the cycle, ir-

respective of the number of stepping relays which may be used for theselection of controls after the station is selected. With relay SOpicked up after station selection, additional impulses are effective tooperate only those stepping relays at this particular station, since thecircuit for the stepping relays is by way of front contact 2I3 of relayS0 It will be understood that the contacts similar to H3 of otherstation relays which are dropped during the cycle, are effective todiscontinue the stepping relay operation at those stations.

During the third on period, the No. 3 control impulse is as determinedby lever 2SML of Fig. 4A being actuated to its right hand position. Thisimpulse in line N actuates relay IF to the right and closes a circuitfor energizing relay SMR. which extends from front contact 208 of relayS0 front contact 205 of relay 3V contact I91 of relay IF in its righthand dotted position, control bus conductor I9l, front contact 2 I4 ofrelay 3V and upper winding of relay SMR to This actuates relay SMR tothe right, which closes a circuit for energizing the motor to operatethe track switch TS to its normal locked position.

It will be obvious that lever ZSML'in its alternate position iseffective to energize relay ENC, which applies a impulse to line N atthe third step for actuating relay IF to the left. This transfers theabove described circuit from at contact I91 of relay IF to the controlbus and thence through conductor I90 and front contact 2H5 of relay 3Vto the lower winding oi relay SMR This circuit is effective to energizerelay SMR, in the opposite sense for actuating the switch machine motorin the proper direction to operate the track switch TS to a reverselocked position. In a similar manner, any num' ber of additional stepsmay be provided for trans mitting additional controls to the selectedfield station for governing the signals and such other devices as may benecessary.

It will be understood thatcontacts 2 I4 and 2 I5 on relay 3V are typicalof the arrangement used when additional steps are provided. For example,wires I90 and I9I will be connected through back contacts of additionalstepping relays starting at the last stepping relay of the series andextending up to contacts such as 2M and M5.

During the selection of an even station alone, odd control relay 00 ofFig. 3A remains deenergized, due to the No. 1 and No. 2 odd. controlconductors which extend through jumpers 250, 25L 252 and 253 to relay OCnot being energized. This is because odd control bus I06 isdeenergizedat front contact I01 of relay ISRP which is down. This results in line Abeing energized continuously from the terminal of battery AB so thatrelays similar to relay 2F at all odd stations remain actuated to theirright hand positions. A series of all impulses applied to line A duringthe station selecting steps of a cycle corresponds to a phantom code anddoes not result in the selection of an odd numbered station.

Assuming that starting button ISB alone is actuated toinitiate a cycleof operations, then relays ISRP and I2CD will be up during the cycle andodd. control bus I06 will be energized. This results in the selection ofthe N0. 1 odd conductor I26, the No. 2 odd conductor I28 and the No. 3odd conductor I30 on the three steps of the cycle respectively. Sinceconductor I26 extends through front contact I21 of relay IZCD and jumper250 to odd control bus 'I25,'the firstimpulse applied to line A (withline B serving as.

the return conductor) is because relay 0C is picked up.

With conductor I28 extending through front contact I29 of relay I'ZCD tojumper 25!, which is disconnected from the 0C bus, relay 0C isdeenergized on the second step so that line A is energized with aimpulse from battery AB. Since conductor I30 extends through frontcontact I3! of relay I2CD to lever ISML and since this lever is showndisconnected from bus I25, relay 00 remains deenergized so that thethird impulse applied to line A is Referring to the field stationcircuits, relay ZF is actuated to the left by the first impulse and acircuit is closed for energizing the station relay (S0 with suitableexponent) at odd station No. 1. This circuit is similar to thatpreviously traced in connection with even station No. 2, except that itextends from a terminal such as H6 at the odd station through conductor294, contact I96 of relay 2F in its left hand dotted position, controlbus jumper 2 I6, front contact 293 of relay IV back contact 292 of relay2V back contact 29! of relay 3V conductor 290 (which corresponds toconductor 29!) associated with even station No. 2) and through a frontcontact similar to 208 of the station relay to The second impulse whichis actuates relay 2F to the right and completes the above describedcircuit by way of contact I96 in its right hand dotted position, controlbus jumper 2", front contact 292 of relay 2V back contact 29! of relay3V conductor 290 and over the remainder of the previously describedcircuit.

The third impulse which is actuates relay 2F to the right and extendswhich is applied to conductor 290 from the front contact similar to 208of the station relay, through front contact 29! of relay 3V contact I96of relay 2F in its right hand dotted position, control bus front contact295 of relay 3V and upper Winding of relay SMR to This actuates relaySMR, to the right for actuating the switch machine at the odd station toits normal locked position, in a manner which is obvious from theprevious description.

It has been mentioned that the 2F relays are not dropped during a cyclefor the selection of an even station. During a cycle for the selectionof an odd station, the 2F relays at the stations are of course shiftedduring off periods, in accordance with the polarities required for thesucceeding on periods. Relay 2F in the control oflice is not droppedduring stepping because the make-before-break contacts 9 and I4 of relay0C prevent the deenergization of relay 2F. This results in back contactI02 of relay 2F remaining open during a control cycle to prevent theenergization of any message relay IM, 2M or SM of Fig. 4B.

During the selection of the No. 1 odd station and the transmission ofcontrols thereto, line N is impulsed with a series of impulses whichcorresponds to an even phantom code and is ineffective to select anyeven station. This series of impulses is provided by relay ENC beingpicked up during all station selecting impulses over a circuit extendingfrom back contact 9! of relay ZSRP, front contact I55 of relay I 2CD,even phantom bus I56, front contact I51 of relay IV, conductor II'! andwinding of relay ENC, to The even phantom bus is also energized for thesame purpose when relays 3SRP and 34GB are up, through back contact I93of relay 4SRP and front contact I68 of relay 340D.

It will be obvious that odd station selection may be accomplished withadditional steps provided in the manner previously mentioned inconnection with even station selection and that additional steps may beprovided for the transmission of additional controls for governingsignals and such other devices as may be necessary.

The jumpers connected as shown in Fig. 4A

indicate the method of odd and even station selection on two steps each.This invention contemplates the use of a different number of stepsduring a cycle for selecting odd and even stations. For example, the No.1 odd conductor I26 might be selectively connected by jumper 250 or 252to bus 00 for selecting station 1 or 3 respectively on the first step.The No. 2 odd conductor I28 could then be connected through switchmachine lever or signal lever contacts to selectively energize bus 00 onthe second step. Then with both the No. 1 even and the No. 2 evenconductors H6 and H8 connected by means of jumpers 254, 255, 256 and 25!as shown, even station selection is accomplished on two steps, afterwhich the No. 3 even wire I20 connected through switch machine or signallever contacts, selectively energizes buses EPC and ENC on the thirdstep. In other words, while jumpers 250 to 251 inclusive are shown forselecting both odd and even stations on two steps, these jumpers may bereplaced by jumper and lever contacts in any desired combination.

Diplezz: transmission.It has been explained how the present inventionfunctions during the transmission of controls to even stations and toodd stations on separate cycles of operation. Diplex transmission iseffected when both storing repeating relays and the associated CD relayare up at the same time when a cycle is initiated.

For example, relays ZSRP, ISRP and I2CD may be up at the start of acycle. In this event, station No. 2 is selected over the N line circuitand station No. 1 is selected over the AB line circuit in the manneralready explained.

Since the N line circuit is used for controlling the stepping at allstations and for the selective conditioning of a polar relay duringstepping at each even station and since the AB line circuit isindependently used for the selective conditioning of a polar relayduring stepping at each odd station, both stations of a pair aresimultaneously selectable and controls may be transmitted to both duringthe same cycle. An explanation oi the effect of simultaneouslyconditioning the two line circuits has been given in connection with thefundamental line circuit arrangement shown in Fig. 1.

Automatic start by a field station.Whenever the system is in the normalperiod or period of blank, it may be initiated from a field station,either in response to some automatic change in trafl'ic conditions or inresponse to the operation of a traii'ic controlling device to a newposition, such as moving the track switch TS from its reverse locked toits normal locked position during a control cycle. Such a change resultsin change storing relay CHS being picked up. It is not believednecessary to show or describe the detailed circuits for picking up relayCHS since this may be accomplished in the manner disclosed in connectionwith relay OHS shown and described in the patent to DeLong et al.,Patent No. 1,852,402 issued April 5, 1932.

The picking up of relay OHS closes a circuit for picking up relay Pextending from back contact 2I8 of relay SA back'contact' 219 of relayFP front contact 220 of relay CHS and upper winding of relay P to RelayP closes a stick circuit for itself extending from back contact 218 ofrelay SA front contact 22l and upper winding of relayP to The actuationof the P relay contacts opens the A line conductor, extending from thecalling station toward the end of the line, at back contact 40. The Aline conductor is connected to the N line conductor at front contact40of relay P in series with resistance 2R the upper winding of relay Land back contact 222 of relay SA.

Since line N is open at front contact 2| of relay EPC in the controloffice, there is no potential applied to this line up to the callingstation. A circuit is effective for energizing the AB line circuit,which extends from the terminal of battery AB, lower Winding of relay2F, back contact 14 of relay 0C, A line conductor 4!, lower winding ofrelay 2E front contact 40' of relay P resistance 2R upper w nding ofrelay L0 back contact 222 of relay SA line N through to the end station,resistance 3R B line conductor, upper winding of relay 2E B lineconductor 33, back contact 9 of relay 0C and upper winding of relay 2Fto the terminal of battery AB.

Current flow in this circuit results in picking up relay 2F in thecontrol office and actuating relay 2F at the field station to the right.It will be understood that all 2F relays at both odd and even stations,are actuated to the right. Helay LO at the calling station is picked up.Since the N line conductor is connected to the B line conductor at theend station, those IF relays farther out theline pick up and effect thepicking up of the SA relays at the respective stations.

The picking up of relay 2F in the control office closes a circuit forpicking up relay FC which extends from back contact 29 of relay SAP,conductor 278, front contact 8' of relay 2F, back contact 89 of relay C,back contact l of relay STR and winding of relay FC, to Relay FC closesa stick circuit for itself through its front contact IE to at backcontact 88 of relay SAP until relay SA is picked up and thereafter to atfront contact 84' of relay SA.

A circuit is now closed for picking up relay STR which extends fromfront contact 1 of relay FC and winding of relay STR, to

A circuit is also closed for picking up relay ENC which extends fromback contact I 66 of relay C, front contact I61 of relay FC and windingof relay ENC, to The picking up of relays ENC and STE applies potentialto line N for energizing all other IF relays connected in this line,including relay l-F Relay SA is picked up to open the circuit includingresistance 2R Other SA relays likewise pick up.

Relay IE (not shown) at the end field station is effective when actuatedto pick up relay FP (not shown), which in turn picks up relay SA bymeans of circuits which will be obvious from those shown. in connectionwith the No. 2 station. This establishes the line circuit arrangement asillustrated in Fig. 1 (assuming front contacts 27 and 28 of relay SApicked up). The continuity of the A line conductor at the callingstation is established at polar contact 2250f relay IF so that this lineconductor is pieced out irrespective of its open condition at backcontact 49 of relay P The station relays (S0 with suitable exponent) arepicked up at all odd stationsby means of a circuit, similar to thatextending through contact I96 of relay 2E in its right hand dottedposition. The station relays at even stations are picked up overcircuits similar tothat previously ing each on period from the terminal.

of battery AB because relay 00 remains deenergized throughout the cycle.Therefore, the IF relays at the stations are actuated to the left inresponse to a series of impulses and the ZF-relays areactuated to theright in response to a series of impulses applied to line A. It will berecalled that a series of all impulses, positioning the 2F relays to theright, corresponds to a phantom code and does not select any odd stationand that a series ofall impulses, which position the. IF relays to theleft, also corresponds to a phantom code combination and does not effectthe selection of an even station.

7 After relay- SA is picked up at the calling station, a circuitis-closed forsticking the lockout relay which extends from front contact221 of relay SA front contact 228and lower winding of relay L0 to Thepicking up of relay IF in. the control office, due to the energizationof line N, is followed by the pick-- ing up. of relays FP, SA, SAP andEP inv the manner previously described in connection. with.

a control cycle. The system is now stepped through the cycle aspreviously described and.

during the off periods between the energized periods. of thelinecircuit, the A and B line conductors are conditioned for transmittingindication code combinations.

Registration of a field station.--It. will now be assumed that thesystem is advanced through a cycle and an explanation-will be given ofthe.

manner the. field station (illustrated in Figs. 5 and 6) is registeredin the control office The AB. line circuit is impulsed during the firstoff. period (following the conditioningperiod above explained) once or"twice or not at all, as determined by the connections of jumpers.

28B and 281. With jumper 280 connected to. the

No. 1 pulse bus 299 as shown: and with jumper 28! disconnected as shown,the AB' line circuit is impulsed once. It will be recalled that relay Pwas picked up to start the cycle. It is stuck up until relay SA picksup, when its energizing circuit is opened at back contact 2|8' of relaySA P is. established when relay SA picks upwhich extends from frontcontact 282 of relay FP front' contact 283 of relay SA front contact 284of relay'LO back contacts 285, 286" and 281 of relays VP 3V and 1Vrespectively, the No. 1 conductor, jumper 280,. No. 1 pulse bus 299 andupper winding of relay P to.

With relay P picked. up and its back contact 49. open, the AB linecircuit is deenergized'when. relay [F is dropped. at the start of thefirst.

foff? period, by the opening of its contact.225.

Another energizing circuit for relay

